This invention relates to a rotatably supported roll, which is adapted to form a nip with another roll in a film production line or the like.
Rolls of the described type are known, and they are used in (two and multi-roll) systems to compensate for the bending of conventional, cylindrical rolls along the nip between the rolls, and to adjust a uniform distribution of the pressure over the entire length of the nip between the rolls (see, German trade journal tpi 1991, July, pp. 647-649). In this instance, the bulging or camber of the roll jacket in the axial direction of the roll is calculated and constructed for a type of load which is determined by certain parameters. It is therefore operational only for this special operating condition and, when load conditions change, it would have to be adjusted to these new load conditions. However, cambered rolls are mostly solid core rolls, the jacket of which is turned and ground with the determined bulging in a costly machining process. They represent thus an essentially rigid system, which does not permit an adjustment to changed operating parameters.
To compensate for the bending of the rolls due to a load in the nip between the rolls, other constructional solutions have been previously proposed. In these roll systems, for example, the roll jacket is supported by hydraulic forces on a stationary shaft ("floating roll" or "S roll", see Melliand Textilberichte 39/1(1958), pp. 88-90; and 53/8(1972), pp. 935-940; or also "Nipco roll"), or it is intended to accomplish by the arrangement of several pressure zones and their .individual pressure application that the bending line of the roll can be adapted to the respective operating condition (DE 31 05 175 C2; German journal Melliand Textilberichte 67/3(1986), pp. 184-188).
The known systems, in which a bending is equalized by a hydraulic support of the roll jacket, are technically very costly, and the costs of investment for such systems are therefore very high. As a result they have been realized essentially only in the construction of calendar lines. Furthermore, they are unsuitable for additional tasks, for example, when it is necessary to actively cool the roll jacket in a film casting line or in a calendar, so as to dissipate a large amount of heat, so that the resin is cooled below its solidification point and solidified on the roll.
It is the object of this invention to provide a roll of the described type, in which the bulging of the roll jacket may be adjusted in a controlled manner and can be adapted for operation with different operating parameters, without removing the roll.